The present invention relates to a liquid crystal display device, and in particular, to a circuit for driving a matrix liquid crystal display device.
Matrix liquid crystal displays are known in the art. Reference is made to FIGS. 1 through 3 in which a conventional matrix liquid crystal display is provided. A liquid crystal panel generally indicated as 1 is composed of a liquid crystal layer 5, a first substrate 2 and a second substrate 3 for sandwiching the liquid crystal layer 5 therebetween. A plurality of common electrodes Y1 through Y6 are oriented on substrate 2 in the horizontal direction and a plurality of segment electrodes X1 through X6 are formed on substrate 3 in substantially the vertical direction to form a matrix. Each intersection of common electrodes Y1 through Y6 and segment electrodes X1 through X6 forms a display dot 7. Display dots 7 marked by the hatching indicate an ON state, and the blank dots 7 indicate an OFF state. The dot structure of liquid crystal panel 1 is limited to a six by six matrix for simplicity however, in exemplary embodiments the number of dots of liquid crystal panel 1 may be much greater.
The voltage standard method is conventionally used for driving the prior art matrix liquid crystal display device. A selected voltage or non-selected voltage is sequentially applied to each of common electrodes Y1 through Y6. The period required to apply the successive selected voltage or non-selected voltage to all the common electrodes Y1 to Y6 is one frame.
Simultaneous to the successive application of the selected voltage or non-selected voltage to each common electrodes Y1 through Y6, an ON voltage or OFF voltage is applied to each segment electrode X1 through X6. Accordingly, to turn a display dot 7, the area in which one common electrode intersects one segment electrode, to the ON state, an ON voltage is applied to a desired segment electrode when the common electrode is selected by providing a selected voltage to the desired common electrode. Similarly if the display dot is turned OFF, the OFF voltage is applied to the desired segment electrode.
Reference is now also made to FIGS. 2 and 3 in which examples of the actual driving waveforms (waveform of the applied voltage) applied at the electrodes are provided. FIG. 2A shows the segment voltage waveform applied to segment electrode X5 over time. FIG. 2B shows the common electrode waveform applied to common electrode Y3 over time. FIG. 2C shows the voltage waveform applied for producing the ON state at display dot 8, the intersection of segment electrode X5 and common electrode Y3.
FIG. 3A shows the segment voltage waveform applied to segment electrode X5 over time. FIG. 3B shows the common voltage waveform applied to common electrode Y4 over time. FIG. 3C shows the voltage waveform applied to the display dot at the intersection of segment electrode X5 and common electrode Y4 to produce the OFF state.
In FIGS. 2 and 3, F1 and F2 indicate the frame period. During frame period F1,
selected voltage=V0, PA1 non-selected voltage=V4 PA1 ON voltage=V5, PA1 OFF voltage=V3 PA1 selected voltage=V5, PA1 non-selected voltage=V1 PA1 ON voltage=V0, PA1 OFF voltage=V2,
During frame period F2,
wherein; EQU V0-V1=V1-V2=V EQU V3-V4=V4-V5=V EQU V0-V5=n V
(n is a constant).
Accordingly, by changing the polarity of the voltage which is applied to display dots 7 during frame periods F1 and F2, alternating driving is accomplished. It follows that whether the display dot 7 is ON or OFF depends on whether the ON voltage or OFF voltage is applied to the desired segment electrode when the selected voltage is applied to the intersecting common electrode corresponding to the desired display dot. This driving method is the voltage standard means used in the prior art.
The prior art structure and driving method has been less than satisfactory. When matrix liquid crystal display 1 is driven by the above conventional voltage standard method, the uniform rectangular waveforms illustrated in FIGS. 2 and 3 are not actually applied to display dots 7. Distortions in the applied waveforms occur. A first reason for the distortion is that each display dot 7 has an inherent electrical capacity based on the area of each dot 7, the thickness of the liquid crystal layers, the dielectric constant of the liquid crystal materials and so on. Secondly, both the common electrode and segment electrode are formed of a transparent conductive film having a surface resistance of about several tens of ohms as well as fixed electrical resistance. Therefore, even if the uniform rectangular waveforms as shown in FIGS. 2 and 3 are applied by the driving circuit, the waveform which is actually applied to the display dots becomes deformed and cross talk results. As a result, it becomes necessary to generate the difference of the effective voltage of the waveform which is applied to each display dot, resulting in the generation of contrast cross talk.
Observation has demonstrated that deformation of the voltage waveform being applied to the display dots occurs based upon relationship dependent on the pattern of the characters or drawings which is displayed by the liquid crystal display device. Secondly, the change of the effective voltage based on the deformation of the voltage waveform which is applied to the display dots causes the contrast crosstalk.
1. The First Mode (Zebra Crosstalk)
Reference is now made to FIGS. 1, 4, 5, and 6A through 6C wherein zebra crosstalk is depicted. For simplicity of explanation, the common electrodes Y1 through Y6 are sequentially selected from the first common electrode Y1 to the sixth common electrode Y6, again returning to the first common electrode Y1. Additionally, liquid crystal panel 1 is a positive display wherein the greater the effective voltage applied to the display dots 7, the darker the display dot. A scale is provided in FIG. 4 to indicate relative darkness. This type of display is used for each explanation unless otherwise indicated.
If the display of FIG. 1 is desired and the inputs of FIGS. 2 and 3 are provided, the crosstalk of the display contrast as shown in FIG. 4 actually occurs in the liquid crystal display device 1. As can be seen, segment electrodes X1 through X4 receive identical inputs. The segment voltage waveform at the display dots portion of segment electrodes X1 through X4 is shown in FIG. 5A, the common voltage waveform applied at the display dot portion of the common electrode Y3 is shown in FIG. 5B. The voltage waveform applied at the display dots located at the intersections of segment electrodes X1 through X4 and common electrode Y3 is shown in FIG. 5C. The voltage waveforms applied to the four display dots will differ from each other slightly. However, this slight difference can be ignored here.
A spike shaped deformation of the voltage waveform occurs at the non-selected voltage level of the common voltage waveform as shown in FIG. 5B. The relationship between the direction and the size of the spike shaped voltage and the display pattern is as follows. Generally, when the selection of the successive common electrode moves from the nth common electrode to the (n+1)th common electrode, the number of segment electrodes to which the ON voltage is successively added is a, the number of segment electrodes to which the OFF voltage is successively applied is b, the number of segment electrodes to which a voltage is applied by switching from the ON voltage to OFF voltage is c and the number of segment electrodes to which the voltage is added by switching from the OFF voltage to ON voltage is d. The number of ON dots 7 on the nth common electrode is N.sub.ON. The number of OFF dots 7 on the nth common electrode is N.sub.OFF and the number of ON dots 7 on the (n+1)th common electrode is M.sub.ON while the number OFF dots on the (n+ 1)th common electrode is M.sub.OFF. The relationship between the segmented electrodes and common electrodes is as follows: EQU N.sub.ON =a+c, EQU N.sub.OFF =b+d EQU M.sub.ON =a+d, EQU M.sub.OFF =b+c EQU N.sub.ON +N.sub.OFF =M.sub.ON +M.sub.OFF =K
K is a constant and equal to the total number of display dots on each common electrode Y.
A value of I equal to the difference in ON dots between successive segment electrodes is defined as follows: ##EQU1## so, when the value of I is negative, the direction of the spike shaped voltage is in the direction of the ON voltage. On the other hand, where the value of I is positive, the direction of the spiked shaped voltage is in the direction of the OFF voltage. The size of the spike increases in accordance with the absolute value of I.
In other words, when the number d of segment electrodes in which the applied voltage switches from the OFF voltage to ON voltage is larger than the number c of segment electrodes in which the applied voltage switches from the ON voltages to OFF voltage, the spike shaped voltage occurs on the common voltage waveform in the direction of the ON voltage. In contrast thereto, when the sign of I, which is the difference between c and d, changes the spike shaped voltage occurs in the direction of the OFF voltage. Additionally, the value of the spike shaped voltage corresponds to the absolute value of I.
As shown in FIGS. 5A and 5B, when the relationship between the change of the segment voltage waveform and the direction of the spike shaped voltage of the common voltage waveform on the non-selected voltage are in-phase, a rounded corner occurs in the voltage waveform of the voltage applied at the display dots (FIG. 5C). The longer the in-phase period, the smaller the effective voltage value of the applied waveform, resulting in the displayed color becoming very light.
Reference is now made to FIG. 6 which illustrates the change of the segment voltage waveform and the direction of the spike on the common voltage waveform when the waveforms are out of phase. FIG. 6A shows the segment voltage waveform applied at the display dot portion of the segment electrode X5 of display 10. FIG. 6B shows the common voltage waveform applied at the display dot 7 portion of the common electrode Y3. FIG. 6C shows the combined voltage waveform which is applied to the display dot at the intersection of segment electrode X5 and common electrode Y3. As shown, where the relationship between the change in the segment voltage waveform (FIG. 6A) and the direction of the spike shaped voltage of the common voltage waveform of the non-selected voltage (FIG. 6B) are out of phase, a spike shaped voltage is generated in the combined voltage waveform applied to the display dots 7 (FIG. 6B), thereby increasing the effective value of the applied voltage. The longer the out of phase period, the larger the effective value, resulting in a darkening of the displayed color. Therefore, display dots 7 on segment electrodes X1 to X4 become light, and the display dots on the segment electrode X5 become dark regardless of the applied ON state or OFF state voltages. The darkness of display dots 7 on segment electrode X6 become a color of intermediate degree between the above on segment electrodes X1 to X4 and those on X5.
2. The Second Mode (Horizontal Crosstalk)
Reference is now made to FIGS. 7 through 10 in which a desired pattern is illustrated. FIG. 7 illustrates a display 11 on which a horizontal crosstalk pattern is displayed. Display 1 is the same as liquid crystal panel 1. The actual contrast crosstalk generated by display 11 is shown by display 12 of FIG. 8.
Display dot 7 acts as a capacitor. The capacity of this capacitor has a different value in the ON state than in the OFF state. The value of the capacitance in the ON state is larger than the capacitance in the OFF state. This occurs because the liquid crystal 5 acts as an anisotropic dielectric and the resulting alignment change occurs between the ON state and OFF state. Accordingly, the capacitance of all dots 7 on common electrode Y2 having many ON dots 13 is larger than that on common electrode Y4 having a few ON dots 13. Since common electrodes have the same circuit resistance, the rounded waveform generated in the voltage waveform of common electrode Y2 becomes larger.
FIG. 9A shows the segment voltage waveform over time applied at the display dot portion on the segment electrode X1 of display 11. FIG. 10B shows the common electrode waveform over time applied at the display dot portion on the common electrode Y2. FIG. 9C shows the combined voltage waveform over time applied to dot 7 at the intersection of segment electrode X1 and common electrode Y2.
FIG. 10A shows the segment voltage waveform over time applied at the display dot portion on the segment electrode X1 of display 11. FIG. 10B shows the common voltage waveform over time applied at the display dot portion on the common electrode Y4. FIG. 10C shows the combined voltage waveform over time which is applied to the dot at the intersection of segment electrode X1 and common electrode Y4.
As can be seen from a comparison of FIG. 9B and FIG. 10B, the waveform of common electrode Y2 which has many ON dots is more rounded when a change from the non-selected voltage to selected voltage occurs. This area is marked by the hatched area. As can be seen by comparing FIG. 9C with FIG. 10C the voltage effective value of the waveform which is applied to dots 13 on common electrode Y2 also decreases by the hatched area. Accordingly, the color produced at each display dot 7 of common electrode Y2 having many ON dots 13 becomes very light. Thus, if the number of ON dots on each common electrode is represented by Z, the larger the value of Z of the common electrode, the lighter the displayed color.
3. The Third Mode (Vertical Crosstalk)
Reference is now made to FIGS. 12 through 17C in which vertical crosstalk is illustrated. The pattern of display 14 is actually displayed as display 15 due to vertical crosstalk. the segment voltage waveform applied at the display dot portion on segment electrode X6 is shown in FIG. 13A. The common voltage waveform applied to the display dot portion on the common electrode Y2 is shown in FIG. 13B. The combined voltage waveform which is applied at the display dot at the intersection of segment electrode X6 and common electrode Y2 is shown in FIG. 13C. Further, FIGS. 14A through 14C show each voltage waveform on segment electrode X5 and common electrode Y2 and the voltage waveforms which are combined to form the actual waveform at the display dot at the intersection of segment electrode X5 and common electrode Y2.
A second example of vertical crosstalk is now described. The segment voltage waveform applied at the display dot portion of segment electrode X6 is shown in FIG. 17A. A desired pattern is input to produce the pattern on display 15. However, due to vertical crosstalk a pattern such as that of display 16 results. The common voltage waveform applied at the display dot portion of common electrode Y3 is shown in FIG. 17B. FIG. 17C shows the combined voltage waveform which is applied to the display dot at the intersection of segment electrode X6 and common electrode Y3. Similarly, FIGS. 18A through 18C show each voltage waveform applied at segment electrode X5, common electrode Y2 and the combined voltage waveform applied at display dot 7 at the intersection of segment electrode X5 and common electrode Y2.
The non-selected voltage level of the common voltage waveform during the displaying of the pattern of display 14 having many ON dots varies in the ON voltage direction as shown in FIG. 13B. Conversely, the non-selected voltage level of the common voltage waveform of display 15 having few ON dots varies in the OFF voltage direction as shown in FIG. 17B.
Where there are many ON dots, the variation is caused because each of common electrodes Y1 through Y6 is electrically connected to the segment electrode to which the ON voltage is applied through the condenser of display dots to a greater extent than to the segment electrode to which the OFF voltage is applied. The reason for this phenomenon is unclear, but it may occur due to a lack of sufficient output impedance of the power circuit relative to the load of the liquid crystal panel. The relationship for the generated voltage shift is described below.
For all display dots 7 of displays 14 and 15 T is the number of ON dots and L is the number of OFF dots. A value T' is defined as T'=T-L when T' is positive, the non-selected voltage level varies in the ON voltage direction. On the other hand, when T' is negative the non-selected voltage level varies in the OFF voltage direction. The size of the variation increases in accordance with the absolute value of T'.
Where the pattern includes many ON dots 13 as shown in display 14, the difference between the OFF voltage and the non-selected voltage becomes large and the difference between the ON voltage and the non-selected voltage becomes small. Therefore, comparing the voltage waveform (FIG. 14A) which is added to display dots 7 on segment electrode X5 of display 15 (FIG. 12) having no ON dot 13, with the voltage waveform FIG. 13A which is added to display dots 7 on segment electrode X6 having ON dot 13, illustrates that the effective combined voltage which is applied to display dot 7 on the segment electrode X5 is larger for the portion marked by the hatched area (FIG. 14C), thereby making the display dots on the segment electrode X5 dark when they should be blank.
Similarly, where the display has few ON dots 13 such as display 15, the difference between the ON voltage and the non-selected voltage becomes large, and the difference between the OFF voltage and the non-selected voltage becomes small. Therefore, comparing the voltage waveform which is provided to display dots 7 by segment electrode X6 including ON dot 13, and the voltage waveform which is provided to display dots 7 on the segment electrode X5 having no ON dot 13, the effective voltage which is provided to the display dots on the segment electrode X6 is larger than that of electrode X5 for the period marked by the hatched area (FIG. 17C) resulting in a dark display dot on segment electrode X6.
4. The Fourth Mode (Inversion Crosstalk)
Reference is made to FIGS. 18 through 21 in which inversion crosstalk is illustrated. A desired pattern is input to a display 17 (FIG. 19), but in reality appears as the pattern on a display 18 (FIG. 20) due to inversion crosstalk. FIG. 21A shows a segment voltage waveform provided at the display dot portion o segment electrode X6. FIG. 21B shows a common voltage waveform provided at the display dot portion on common electrode Y2. FIG. 21C shows a combined voltage waveform which is provided to display dot 7 at the intersection of segment electrode X6 and the common electrode Y2. FIG. 22 shows the combined voltage waveform provided to display dot 7 at the intersection of segment electrode X5 and common electrode Y2.
Reference is now made to FIGS. 23 through 26 wherein a second example of inversion crosstalk is provided. A pattern is input to appear as display 20 (FIG. 23), but in reality appears as the pattern of display 19 (FIG. 24) due to inversion crosstalk. FIG. 25A shows a segment voltage waveform provided at the display dot portion of segment electrode Y6. FIG. 25B shows a common voltage waveform provided at the display dot portion of common electrode Y2. FIG. 25C shows the combined voltage waveform which is provided at display dot 7 at the intersection of segment electrode X6 and common electrode Y2. FIG. 26 shows a combined voltage waveform provided by electrodes Y2 and X5 to display dot 7 at the intersection of segment electrode X5 and common electrode Y2.
The time period of switching between frame periods, i.e. before or after the switching from F1 to F2 of FIG. 21 and FIG. 25 is known as the inversion. As shown in FIG. 19 when the number of segment electrodes in which the voltage applied to the segment electrode is an ON voltage before and after the inversion (only the 6th segment electrode X6 in FIG. 19) is less than the number of segment electrodes in which the voltage applied to the segment electrode is an OFF voltage before and after the inversion (the five segment electrodes X1 to X5 in FIG. 19), a rounded waveform as is shown in FIG. 21B occurs at the time of inversion.
Therefore, when the pattern as shown in FIG. 19 is displayed, the rounded waveform occurs in the common voltage waveform as shown in FIG. 21B at the time of inversion.
Simultaneously, the voltage waveform applied to the segment electrode X6 (FIG. 21A) applied to display dots 7 on segment electrode X6 for changing from an ON voltage to an ON voltage before and after the inversion, generates a spike shaped voltage as shown in FIG. 21C, thereby increasing the effective voltage making the display dark. On the other hand, for the voltage waveform which is applied to display dots 7 of segment electrodes X1 through X5 for changing from an OFF voltage to an OFF voltage before and after the inversion, the rounded portion of the waveform as shown in FIG. 22 occurs, thereby decreasing the effective voltage, thus lightening the display.
Conversely, in display 20 (FIG. 23) the spike shaped voltage is generated in the common voltage waveform as shown in FIG. 25B at the time of inversion. Simultaneously, when the applied waveform changes from an ON voltage to an OFF voltage before and after the inversion, a rounded section (FIG. 25C) is generated in the voltage waveform which is applied to display dots 7 on segment electrodes X1, X2, X3, X4 and X6, thereby decreasing the effective voltage and further lightening the displayed color. Additionally, when the voltage applied to the display dots on the segment electrode X5, switches from an OFF voltage to an OFF voltage before and after the inversion, a spike shaped voltage (FIG. 26) is generated thereby increasing the effective voltage, darkening the displayed color.
The above relationship is defined as follows. The number of segment electrodes switching from an ON voltage to an ON voltage at the time of inversion is a. The number of segment electrodes switching from an OFF voltage to an OFF voltage at the time of inversion is b. The number of segment electrodes switching from an ON voltage to an OFF voltage is c. The number of segment electrodes switching from an OFF to an ON voltage is d. Further, the number of ON dots on the common electrode (Y6, FIGS. 19 and 23) which is selected just before the inversion is N.sub.ON and the number of OFF dots on the common electrode is N.sub.OFF while the number of ON dots on the common electrode (Y1, FIGS. 19 and 23) which is selected just after the inversion is M.sub.ON and the number of OFF dots on the common electrode is M.sub.OFF. EQU N.sub.ON =a+c, EQU N.sub.OFF =b+d EQU M.sub.ON =a+d, EQU M.sub.OFF =b+c EQU N.sub.ON =N.sub.OFF =M.sub.ON +M.sub.OFF =K
K is a constant representing the number of display dots on each common electrode. Wherein, ##EQU2## If the value of F is negative, at the time of the inversion, the rounded waveform occurs when the non-selected voltage changes on the common electrode. Conversely, if the value of F is positive, the spike shaped voltage occurs in the direction of the ON voltage. The value the applied voltage increases in accordance with the absolute value of F. This introduces the display crosstalk as mentioned above.
The general crosstalk problem has been well known in the art. A method for correcting crosstalk is also known in the art and is illustrated in Japanese Laid-Open Patent Nos. 31825/87, 19195/85 and 19196/85. The method consists of reversing the polarity of the voltage which is applied to the liquid crystal panel a predetermined number of times per frame. This method is known as the line reverse driving method.
However, this method has been less than satisfactory. The line reverse driving method corrects only one mode of crosstalk (zebra crosstalk) of the plurality of cross talk modes. As mentioned above, there are four modes of crosstalk in the display relating to the mechanism which arise due to changes of the voltage waveform. Accordingly, the crosstalk of the display contrast is not completely removed.
A system for driving a liquid crystal display which would solve the uneven contrast of the display by changing a portion of a driving voltage waveform applied to a liquid crystal panel in accordance with the characters and the designs displayed is known from Japanese Patent Application No. 63-159914. This system amends the unevenness in contrast by changing a portion of the driving voltage waveform in accordance with the display characters or designs. However, this system suffers from the disadvantage that it does not include a parameter related to an ambient temperature or the temperature of a liquid crystal display. Because the liquid crystal display characteristics depend on temperature, proper amendment of the voltage waveform and resulting display cannot be effected over a wide range of temperatures.
Reference is first made to FIG. 83 wherein the power circuit for producing a voltage waveform which corrects the uneven horizontal cobwebbing display as known in Japanese Patent Application No. 63-159914 is provided. A plurality of resistors 6101 through 6105 are serially connected and a voltage V0N and V5N is supplied at the end of the resistors providing a series of voltage dividers thereof and an operating voltage V.sub.op defined as V0N-V5N. The voltage at the end of each respective resistor 6101 through 6105 is defined as V1, V2, V3, V4 and V5N. A respective Voltage follower circuit 6106 through 6109 is provided at the end of resistors 6101 through 6105 to reduce the impedances of voltages V1, V2, V3 and V4.
Voltage V0N and V5N are operated on by mirror-like structures. A constant power source 6110 is provided at voltage line 6170 and across a pair of resistors 6112, 6128 provided in series which serve to divide the voltage output by constant power source 6110. The divided voltage is a reference voltage. An inverting amplification circuit 6116 receives as one input the divided voltage from the voltage divider provided by resistor pairs 6112, 6128. At its other input, circuit 6116 receives the voltage V1 produced by voltage follower circuit 6106, input to reversible amplification circuit 6116 through a resistor 6117. A resistor 6118 is coupled to a resistor 6117 at the input of amplification circuit 6116 at its one end and at the output of amplification circuit 6116 at its other. Amplification circuit 6116 produces an inverted voltage V1 which has been biased by the reference voltage. A resistor 6122 is coupled to the output of amplification circuit 6116 and resistor 6118 at one end and a diode 6124 at its other end which is coupled to a voltage line 6171 carrying voltage V0N. Resistor 6122 and diode 6124 comprise a circuit for keeping the output voltage of reversible amplification circuit 6116 at a level no greater than V0N. A voltage follower circuit 6126 receives th output of reversible amplification 6116 and outputs voltage V0U.
Similarly, a constant voltage power source 6111 is coupled to a voltage line 6170 and across pair of resistors 6113, 6129 coupled in series to provide a divided reference voltage. An inverting amplification circuit 6119 receives the divided reference voltage at one input and the voltage V4 output by voltage follower circuit 6109 input through a resistor 6120 at a second input. A resistor 6121 is connected to resistor 6120 at the input to inverter amplification circuit 6119 at its one end and the output of amplification circuit 6119 at its other end. Inverting amplification circuit 6119 outputs an inverter voltage V4 based on the reference voltage produced between resistor 6120 and 6121.
A resistor 6123 coupled to the output of inverting amplification circuit 6119 is coupled to a diode 6125 to form a circuit for preventing the output voltage of amplification circuit 6119 to be greater than V5N. A voltage follower circuit 6127 receives the output of amplification circuit 6119 and outputs a voltage V5L.
Reference is now made to FIG. 84 in which a graph representing the voltages produced based on the correction suitable at 25.degree. C. using the prior art construction and the ideal correction at a higher temperature, as a function of V.sub.op, is provided. Voltage V0U based on the correction suitable at 25.degree. C. is denoted by graph line 6151. The voltage V5L based on the correction suitable at 25.degree. C. is represented by the line 6152. These voltages are to be compared with the representation of the ideal voltages based on experimental data shown in FIG. 82 in which the ideal voltage represented at each temperature is provided. Lines 6131 and 6132 on the graph represent voltages V0U and V5L at a temperature of 50.degree. C. Points 6133 and 6134 denote voltages V0U and V5L at a temperature of 25.degree. C. Points 6135 and 6136 represent the respective voltages V0U and V5L at a temperature of 0.degree. C. As can be seen from comparing the graphs in FIG. 82 and FIG. 84, the voltages V0U and V5L differ greatly from the ideal except at the temperature of 25.degree. C. As shown in FIG. 84, on which line 6135 from FIG. 82 representing the ideal voltage V0U at 0.degree. C. has been added, when V.sub.op changes from Point X to Point Y with a change of temperature, the prior art arrangement produces an excessive correction voltage represented by Point A, while the ideal value of the correcting voltage is represented by Point B. Accordingly, this illustrates how the prior art has been unable to control the voltages over a wide range of temperatures.
Accordingly, a mechanism for driving a liquid crystal display which overcomes the limitations of the prior art by correcting for crosstalk over a wide range of temperatures is desired.